D–A–π–A organic dyes with tailored green light absorption for potential application in greenhouse-integrated dye-sensitized solar cells

In this paper, we present the design and synthesis of three organic dyes specially developed for the fabrication of dye-sensitized solar cells for application in greenhouses cladding. The dyes (BTD-DTP1–3) are based on a benzothiadiazole (BTD)–dithienopyrrole (DTP) scaffold, and were assembled by using direct arylation reactions, allowing significant reduction of the number of synthetic and purification steps compared to classic cross-coupling procedures. Thanks to their structural design, the dyes absorb light in the green part of the visible spectrum while allowing good transmittance in the red and blue regions, thus ensuring high compatibility with light absorption by plants. Dye-sensitized solar cells built with the three dyes provided energy conversion efficiencies (ECEs) comparable or even superior to those obtained with the reference Ru-based dye N719, especially when using a thin and semitransparent TiO2 layer (up to 8.77%). The photovoltaic performances are discussed considering the need to reach the best compromise between good ECE values and high levels of weighed transparency against the main plant photoreceptors.